Babies' flexible squeals may enable them to talk later

Communication advance in months after birth tied to language learning

Babies take a critical step toward learning to speak before they can say a word or even babble. By 3 months of age, infants flexibly use three types of sounds — squeals, growls and vowel-like utterances — to express a range of emotions, from positive to neutral to negative, researchers say.

Attaching sounds freely to different emotions represents a basic building block of spoken language, say psycholinguist D. Kimbrough Oller of the University of Memphis in Tennessee and his colleagues. Any word or phrase can signal any mental state, depending on context and pronunciation. Infants’ flexible manipulation of sounds to signal how they feel lays the groundwork for word learning, the scientists conclude April 1 in the Proceedings of the National Academy of Sciences.

Language evolution took off once this ability emerged in human babies, Oller proposes. Ape and monkey researchers have mainly studied vocalizations that have one meaning, such as distress calls.

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